Ok, I know I'm probably not the first to do this, but i thought I'd share my system for heating my strike water while I sleep. There are calculators online that will let you figure out how long the water takes to heat, but I found I still needed to do some math in converting units, etc, then I ALSO had to count back from when I wanted to mash in. So I whipped up a spreadsheet to let me know when to set my timer for.

There are more powerful units which can heat the water faster, but then you have to worry about the amperage of your breakers and any extension cords you're using, not to mention the timer below. This one is cheap, safe, and does the job while playing nicely with standard circuits and cords.

Finally, grab my spreadsheet file and calculate what time to set your timer to kick on. It is pretty self-explanatory, except for the thermal loss cell. In real life, while you're heating your strike water, you're also losing some heat due to the imperfect insulation of the vessel. This box gives you the chance to use an adjustment factor if you are finding you're not quite at target temp at the expected mash-in time. (Note there are imperial and metric sheets)

{example: if you start with 45F water and want 170F, but you're finding the heater only got you to 160F; that means instead of a rise of 125F, you got a rise of 115F. 125/115 = 1.086. I would punch in 1.086 to adjust for the future if I did nothing different to insulate the vessel.}

It's a good idea to plug all this into a GFCI outlet or an external GFCI adapter. Check any cords etc that you use to be rated for 120V, 1000W, at least 8.33A (most household circuits are 15A so you're golden as long as you don't try to power this through a crappy thin extension cord.) As always, read all warning labels and don't run that heater dry!!

Enjoy! I hope others find this useful, I have saved a ton of time crushing my grains the night before and having my strike water heat while I sleep. Now I wake and mash and SWMBO is happier about shorter brew days.
Not to mention I'm saving a ton of propane. The electricity for me to heat 12 gallons of water (some of it I save for my sparge) costs about 40-50 cents! Normally that would have my Top Tier burner running for a good 45 minutes minimum!! Cheers

This is a really good idea. What's different from that water heater, and say, a 1000 W $10 element from Home Depot, other than missing a wire?

Since I mash in a cooler, this sounds like a brilliant way to target a strike temp and avoid trying to account for preheating the tun or accounting from heat loss when pouring in. Gonna give this some thought.

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@Lockwom - Yes, you can build your own heatstick - google "heatstick build" and you'll find lots of results explaining how to do it with sink pipe and JB-weld. Personally, I don't like to tinker with electricity and water and wanted something pre-built that was made for this. Building your own would allow you to go with a higher wattage to shorten the time to heat (and the spreadsheet will allow you to change the wattage), but for me I the 1000W is plenty to do it while I'm in dreamland as it will do 12 gallons in well under 4 hours. I did look at building a higher wattage heatstick (thinking I could maybe heat sparge water this way while the mash proceeded) but then I would need to figure out something different with my circuit breaker. What I do now is heat the 12 gallons to 175-ish, even though I'm only going to mash in with 6-7 gallons. The remaining water is added to with 6 or so more gallons out of the faucet to get back to 12 gallons in the HLT and I usually end up with it being about 110-120F. This still saves me time and propane getting sparge water up to mashout temp.

@Revvy - in reading the Amazon reviews before buying the bucket heater, I believe there were several who stated it did not work well for sous vide. Just an FYI.

@JohnnyJumpUp - True, however the cheapest temp controller build I've seen with a heating stage is roughly $59 just for the controller (I think I put another $15-20 into the build to wire it all up), and this timer is $23. Also, I'm not sure of the amperage one of the temp controllers will handle, I think I read on at least one of them that it was limited to ~3A. Not sure, that was a few months ago.